n → π* transition

https://doi.org/10.1351/goldbook.N04079
An electronic transition described approximately as @P04877@ of an electron from a 'non-bonding' (lone-pair) n orbital to an 'antibonding' π orbital designated as π*.
Source:
PAC, 1996, 68, 2223. (Glossary of terms used in photochemistry (IUPAC Recommendations 1996)) on page 2255 [Terms] [Paper]